1. Field of the Invention
The present invention relates generally to a wireless packet data communication system, and in particular, to a method and apparatus for transmitting signaling information for call control and radio link protocol (RLP) control on a packet data channel (PDCH).
2. Description of the Related Art
Code division multiple access (CDMA) mobile communication systems have been developed from the 2nd generation (2G) standards focusing mainly on voice service to the 3rd generation (3G) standards that enable additional high-rate data service. Since 3G CDMA mobile communication systems support up to 2 Mbps, they transmit up to 256 times more data than 2G CDMA mobile communication systems that support only 9.6 or 14.4 kbps. The high-rate data transmission capability enables various services including high-quality voice service, transmission of moving pictures, Internet browsing, etc.
An initially developed CDMA2000 mobile communication system (CDMA2000 1×) transmits packet data mainly on a supplemental channel (SCH), voice requiring high reliability on a fundamental channel (FCH), and signaling information on a dedicated control channel (DCCH). This is because the FCH and DCCH are designed to have better quality than the SCH.
An advanced 3G CDMA mobile communication that has been proposed particularly to support both voice and high-rate packet data services, CDMA2000 1×EVDV (Evolution in Data and Voice), adopts a PDCH for reliable transmission of voice and packet data at higher rate. Since the PDCH is as good in quality as the FCH and the DCCH, it can deliver information requiring high-rate transmission, for example, signaling information for call control and RLP control together with voice and packet data in the CDMA2000 1×EVDV system. Because existing systems generate signaling information in data units transmittable on the FCH or the DCCH, if a function is added to the systems to generate signaling information in a novel data unit type for transmission on the PDCH and determine whether the current channel is the FCH, DCCH, or PDCH, system functions are complicated and generation of control information to be additionally checked increases time delay and system load.
Moreover, the PDCH is characterized by its variable rate depending on the radio environment of a mobile station (MS) being serviced and the quality of service (QoS) of the service. This implies that one PDCH frame delivers a variable amount of data. In a typical layered communication system, information about the data rate of a physical channel connected for service is managed in a lower layer, without being delivered to an upper layer. Therefore, the upper layer generates data units of a fixed length, each data unit including segmented data, by segmenting a transmission data stream. The lower layer transmits a predetermined number of data units in a physical layer frame of which the length is determined according to the current data rate.
Because it is relatively short, signaling information cannot fill an entire physical layer frame of the PDCH in most cases. Accordingly, it is required that the signaling information be transmitted effectively on the PDCH without modifying existing system configurations, and still minimizing the physical layer frame consumption.